A GaAs/AlAs resonant tunnelling diode (RTD) is incorporated in a 1 mum thick membrane and used as a pressure sensor. The fabrication technology of the membrane is based upon the selective etch of GaAs with AlAs as an etch stop layer. An external pressure introduces stress in the layers of the RTD and modifies the position of the conduction band, the value of the effective mass and the Fermi level. These variations will change the peak current and voltage of the RTD. Measurements at room temperature show that the effect of an applied pressure on a symmetric RTD is asymmetric. This asymmetric is explained theoretically by the difference in the sign of the stress between the top and bottom layers of the RTD.